This fixes https://github.com/flutter/flutter/issues/20746

This adds links to the already existing animated diagrams in the asset-for-api-docs repo.

* [FAB] Updated tooltip touch target.

* Remove "new" keyword

* [FAB] Updated tooltip touch target.

* "long press button edge"

* remove new

* remove new

* put "new" keywords back in

* Remove check for childless tooltip

* Added regression test - tooltip works on edge of FAB which has no child.

Added helper method to find the right edge of a in the tests.

* Changed "find.byType(text)" to "find.text('Add')"

This is follow-up to https://github.com/flutter/flutter/pull/21143.

* Roll engine to 56139397e6ae1257bdabd1ef79ff7aca96c67d4.6

Changes since last roll:
```
56139397e Roll src/third_party/skia 7ba1d64f0706..5f0726b01019 (12 commits) (#6104)
47a1ce0e6 Allow embedders to set the root surface transformation. (#6085)
```

* Roll engine to f3ff83a5db71262d240aa5337a2a9a22c73c4749. (dart roll).

* Add const

* Add ignore analyzer prefer_const_constructors_in_immutables

* Remove workaround for dart-lang/dartdoc#1125

* Update update_icons.dart for optional const and to remove markup stripping workaround

This re-lands commit c594696f.

The original PR was breaking the integration test as while the
gesture was active the AndroidView's parent widget got rebuilt which
disposed the _AndroidViewGestureRecognizer and dropped pointer events
from that point on.

This change adds a unit test that reproduces the failure case, and
fixes it by not rebuilding the _AndroidViewGestureRecognizer if the
list of gesture recognizers did not change.

This reverts commit c594696f.

Pointer events are dispatched to the Android view only if it won
Flutter's gesture arena for the pointer.
Specific gestures that should be dispatched to the android view can be
specified with the gestureRecognizers parameter.

Add a countdown timer picker as part of the Cupertino date picker.

This allows to pass construction parameters for the embedded Android
view from the Dart side.

This allows developers to control the clipBehavior of those buttons.

This reverts commit 8de0e15e and
updates the goldens versoin.

This requires https://github.com/flutter/flutter/pull/20751 to
land first.

* added keyboard functionatliy to android builds

* Added tests

* almost ready for review

* ready for review

* Fixes

* final comments

* final commit

* removing raw keyboard changes

* removing raw keyboard changes

* removing raw keyboard changes

* actual last commit

* fixed the imports

* a few more changes

* A few more changes

* a few changes

* Final changes

* Final changes2

* final actual commit for real

* final actual commit for real2

* final actual commit for real3

* final actual commit for real4

* final

* final 2

* f

* f2

* fin

* fin 2

* fin3

* fin4

Virtual displays must have a non zero size. This was causing a crash:
https://github.com/flutter/flutter/issues/20456

add cupertino localizations abstract class and the default cupertino localizations in US English.

Tabs are now padded by 16.0 on the left and right  (used to be 12.0).

The team captain wins the arena on behalf of the team.
When any of the team members claims victory for the arena the captain
accepts the gesture.

This is used when embeddeding platform views - we allow configuring a
set of gestures that should be forwarded to the platform view.
We add the set of gesture recognizers to a GestureArenaTeam with a
captain, and if the captain accepts the gesture we forward it to the
platform view.

This fixes #20483 by letting InkWell do its own clipping.

PathOp.intersect is not used because we have too many unit tests that rely on clipping (e.g., paints..clipXXX()..drawCircle())

The goldens are updated due to small AA changes of the additional clipPath.

BottomNavigationBar's state needs to update _backgroundColor when its configuration changes.

- remove an //ignore that is no longer needed
- fix some intrinsic methods that used the API incorrectly (shouldn't affect correctness but should make things a tiny bit more efficient)
- add some asserts to help track down bugs quicker
- update a TODO to point to the currently relevant bug
- fix some indenting
- improve the naming of some privates to improve readability